Older egg laying hens have the problem of laying eggs which do not have sufficient shell strength or a sufficient amount of calcium in their shells Said eggs have shells that are too fragile and that easily break during subsequent handling and shipping.
Egg breakage is a serious economic loss at all stages of egg production including, handling at the farm, shipping, and end user handling. It has been estimated that egg breakage may be as high as 5 to 6 percent of total egg production in normal channels in the United States. The economic losses which result from such breakage are clear.
An additional economic problem in older egg laying hens is an increase in bone fragility and decrease in bone strength. Processing of these "spent" hens for inclusion of their meat in soups and other processed foods results in the generation of broken bones and bone splinters which are economically costly to control.
It is known that certain Vitamin D.sub.3 metabolites, namely 1.alpha.-hydroxycholecalciferol and 1.alpha.,25-dihydroxycholecalciferol improve the egg shell strength of older laying hens. Moreover, it is also known that Vitamin D.sub.3 is utilized by the hen for many benefits including leg strength.
It is an object of this invention to provide a poultry feed composition which improves the shell strength of eggs produced by older laying hens and to thereby minimize the economic loss due to egg breakage. It is a further object of this invention to provide a poultry feed composition which supplies to the egg laying hen Vitamin D.sub.3, itself, thereby enabling the egg laying hen to obtain the usual benefits (not attainable through Vitamin D.sub.3 metabolites) of Vitamin D in the diet.
As has been pointed out above, it is known that certain metabolites of Vitamin D.sub.3, namely 1.alpha.-hydroxycholecalciferol and 1.alpha.,25-dihydroxycholecalciferol improve the egg shell strength and bone strength of older egg laying hens. However, the commercial use of these Vitamin D.sub.3 metabolites is severely limited by several inherent characteristics of these compounds, including poor chemical stability and a narrow window between noneffectiveness and toxicity.
More specifically, these Vitamin D.sub.3 metabolites show instability to moisture, oxygen, light, heat, and trace minerals. These just mentioned conditions are unavoidable in feed manufacture.
Furthermore, effective levels of these Vitamin D.sub.3 metabolites for use in improving egg shell strength in older egg laying hens are extremely low as compared to other micro nutrients, and therefore it is extremely difficult to properly distribute these compounds in feed without having portions of the resulting feed contain either too low or too high a concentration. If a portion of the resulting feed contains too low a concentration of the required Vitamin D.sub.3 metabolite, then egg laying hens consuming this portion of the feed compositions will not obtain the benefit of the Vitamin D.sub.3 metabolites, and further will not lay eggs with sufficient egg shell strength so as to avoid the egg breakage discussed above. However, since the above mentioned Vitamin D.sub.3 metabolites are toxic at too high concentrations, those egg-laying hens which feed on portions of poultry feed containing too high a level of the Vitamin D.sub.3 metabolites can become sick or even die.
Additionally, the two above mentioned Vitamin D.sub.3 metabolites are extremely expensive. Accordingly, any attempts to directly mix said Vitamin D.sub.3 metabolites into poultry feeds which result in loss of said Vitamin D.sub.3 metabolites will prove uneconomical.
Prior attempts in the art of incorporating microgram amounts of the above mentioned Vitamin D metabolites into poultry feeds have mainly been conducted on a research level and have consequently circumvented many of the practical considerations necessary to achieve commercial success. These studies typically would incorporate the Vitamin D.sub.3 metabolite by directly adding a freshly prepared oil solution of the metabolite to the animal feeds on a daily basis. This approach allows the investigator individual control of dose administrated but does not provide long term stability protection to the metabolite which is necessary in a practical commercial situation and is part of the present invention.
Prior attempts in the art of incorporating microgram amounts of the above-mentioned Vitamin D into poultry feeds also involved encapsulation of oil soluble microgram amounts of said Vitamin D.sub.3 in an oil/water emulsion. Said oil/water emulsion is then dried by a variety of techniques to produce a particulate composition which is stable when mixed into feed premixes and feeds. The prior art also provides that said particulate compositions can contain antioxidants in the oil phase which contribute to the stability of the Vitamin D.sub.3 and ingredients in the water phase of the emulsion, usually gelatin, gum acacia, modified food starches or casein plus plasticizers like sugars, which serve to retard oxygen diffusion into the oil phase of the emulsion and which also contribute to the structural integrity of the resulting particulate compositions.
As pointed out above, extremely low levels of Vitamin D.sub.3 metabolites are required for improving the egg shell strength of older egg laying hens. Accordingly, if the above described technology for incorporating Vitamin D.sub.3 into poultry feeds was used solely for the incorporation of Vitamin D.sub.3 metabolites the approach would be economically inefficient.
Specifically, the effective levels of Vitamin D.sub.3 metabolites for improving the egg shell strength and bone strength of older egg laying hens is from 1 to 5 micrograms per kilogram of poultry feed. These levels are 10-400 times less on a weight basis than other essential micronutrients like Vitamins D.sub.3 and A which are required for proper nutrition in layers. Therefore, to ensure the proper distribution of Vitamin D.sub.3 metabolites in poultry feeds (both to assure efficacy and to avoid the above discussed possible toxicity), Vitamin D metabolites must be incorporated at levels below 0.10% by weight in the stabilized dehydrated oil/water emulsion described. For example, to obtain 2 micrograms of metabolite per kilogram of poultry feed, a stabilized particulate composition containing 0.10% metabolite would be added to poultry feed at only 2.0 milligrams per kilogram. This level of addition is too low to ensure satisfactory distribution of these Vitamin D metabolites in poultry feeds. At such a low level of addition, distribution of Vitamin D.sub.3 metabolites in poultry feed would be uneven. Those portions of the resulting poultry feed which contain too low a concentration of Vitamin D metabolites would not be adequate for older laying hens to lay eggs of sufficient strength to avoid economic loss through egg breakage or maintain proper bone strength as described above. Conversely, too high a concentration of Vitamin D.sub.3 metabolites in the resulting poultry feed, will result in feed that is toxic and could cause illness or death to egg laying hens.
A preferred concentration of Vitamin D.sub.3 metabolite in a stabilized particulate composition to be used for mixing into poultry feed so as to ensure a proper distribution of Vitamin D.sub.3 metabolite in the final feed mix is about 0.010% by weight. A stabilized preparation at such a low concentration of Vitamin D.sub.3 metabolite is economically wasteful since the cost of carrier materials, processing and quality control is high. It is known that layer feeds will have to contain other essential nutrients like Vitamin D and Vitamin A which are also fat soluble substances. If however, one incorporates the metabolite with other important micronutrient ingredients in the same particle then one can take advantage of the known efficacy of these ingredients and insure the proper distribution of Vitamin D.sub.3 metabolite.
Therefore, a definite need exists for a Vitamin D metabolite containing poultry feed mixture which contains said Vitamin D metabolites at a uniform effective concentration for use in causing older laying hens to produce eggs of greater shell strength. Moreover, the need exists for a poultry feed mixture which does not contain said Vitamin D metabolites in too low a concentration, in which case said laying hens will not produce eggs of sufficient shell strength or bone strength so as to avoid egg breakage or in too high a concentration in which case the Vitamin D metabolites could prove toxic to the egg laying hens. Additionally, there exists a need for a poultry feed composition which incorporates Vitamin D metabolites in such a form as to protect said metabolites from moisture, oxygen, heat, light, and trace minerals. There exists a need for a poultry feed composition which incorporates Vitamin D metabolites placed in the same particle at the time of manufacture in such amounts so as to be economical as compared to the costs of the carrier materials and essential micronutrients like Vitamin D and Vitamin A for said feed compositions. Finally, such a combination product in which the Vitamin D.sub.3 and Vitamin D.sub.3 metabolite are in the same particle at the time of manufacture facilitates the analytical ability to monitor the incorporation of said metabolite onto the feed mixture by analysis for the other essential micronutrients which are known to be present in the invention. This is a significant advantage since the metabolite levels are so low in the feed as to be very difficult to monitor even on a research-much less routine-level.